Université Lille Nord de France, Université de Lille 1, Laboratoire Activité Physique, Muscle et Santé, EA4488, IFR114, IRP2B, Villeneuve d'Ascq, France.
PLoS One. 2012;7(10):e48218. doi: 10.1371/journal.pone.0048218. Epub 2012 Oct 24.
O-N-acetylglucosaminylation is a reversible post-translational modification which presents a dynamic and highly regulated interplay with phosphorylation. New insights suggest that O-GlcNAcylation might be involved in striated muscle physiology, in particular in contractile properties such as the calcium activation parameters. By the inhibition of O-GlcNAcase, we investigated the effect of the increase of soleus O-GlcNAcylation level on the contractile properties by establishing T/pCa relationships. We increased the O-GlcNAcylation level on soleus biopsies performing an organ culture of soleus treated or not with PUGNAc or Thiamet-G, two O-GlcNAcase inhibitors. The enhancement of O-GlcNAcylation pattern was associated with an increase of calcium affinity on slow soleus skinned fibers. Analysis of the glycoproteins pattern showed that this effect is solely due to O-GlcNAcylation of proteins extracted from skinned biopsies. We also characterized the O-GlcNAcylated contractile proteins using a proteomic approach, and identified among others troponin T and I as being O-GlcNAc modified. We quantified the variation of O-GlcNAc level on all these identified proteins, and showed that several regulatory contractile proteins, predominantly fast isoforms, presented a drastic increase in their O-GlcNAc level. Since the only slow isoform of contractile protein presenting an increase of O-GlcNAc level was MLC2, the effect of enhanced O-GlcNAcylation pattern on calcium activation parameters could involve the O-GlcNAcylation of sMLC2, without excluding that an unidentified O-GlcNAc proteins, such as TnC, could be potentially involved in this mechanism. All these data strongly linked O-GlcNAcylation to the modulation of contractile activity of skeletal muscle.
O-N-乙酰氨基葡萄糖基化是一种可逆的翻译后修饰，与磷酸化呈现出动态的、高度调控的相互作用。新的研究结果表明，O-连接的糖基化可能参与横纹肌生理学，特别是在收缩特性方面，如钙激活参数。通过抑制 O-连接的 N-乙酰氨基葡萄糖苷酶（O-GlcNAcase），我们通过建立 T/pCa 关系来研究增加比目鱼肌 O-GlcNAc 水平对收缩特性的影响。我们通过对用 PUGNAc 或噻唑烷二酮（Thiamet-G）处理或未处理的比目鱼肌进行器官培养来增加比目鱼肌活检的 O-GlcNAc 水平，从而建立了比目鱼肌的 O-GlcNAc 化模式。O-GlcNAc 化模式的增强与慢比目鱼肌肌球蛋白纤维钙亲和力的增加有关。糖蛋白模式的分析表明，这种效应仅归因于从去皮活检中提取的蛋白质的 O-GlcNAc 化。我们还使用蛋白质组学方法对 O-GlcNAc 化的收缩蛋白进行了表征，并鉴定出肌钙蛋白 T 和 I 等是 O-GlcNAc 修饰的。我们量化了所有这些鉴定出的蛋白质上的 O-GlcNAc 水平的变化，并表明几种调节性收缩蛋白，主要是快型同工型，其 O-GlcNAc 水平急剧增加。由于唯一增加 O-GlcNAc 水平的慢型收缩蛋白同工型是 MLC2，因此增强的 O-GlcNAc 化模式对钙激活参数的影响可能涉及 sMLC2 的 O-GlcNAc 化，不能排除 TnC 等未鉴定的 O-GlcNAc 蛋白可能参与该机制。所有这些数据都将 O-GlcNAc 化与骨骼肌收缩活性的调节紧密联系起来。
